said by veger:OpenWRT/MLPPP is a fork and it does work on TSI's MLPPP. I've personally tested it with single line setup before switching to cable and it should easily work on the multiple line setup. For it, you'd need TP Link TL-1043ND or Netgear WNDR3700 though. Those are the only 2 platforms it supports (other than x86, which seems to be a non-starter for you).
HI! Thanks for the info, ps, someone told me that Openwrt does Not support two lines at the moment or Not for the router "WZR-HP-AG300H" ( one of the two ).
I see it listed here "http://wiki.openwrt.org/toh/start#buffalo" but I would prefer if someone could confirm it before ordering one.